Micronutrients in Health and Disease: Micronutrients in Clinical Practice

Certain diseases or conditions increase nutrient needs. For example, diseases that cause malabsorption (chronic cholestasis, abetalipoproteinemia, celiac disease, and cystic fibrosis) result in vitamin E deficiency and the need for supplementation.⁶⁵ Clinicians should encourage patients to obtain these nutrients primarily from foods, rather than supplements, due to the presence of other nutrients in whole foods and their potentially synergistic effects.⁶⁶ For example, vitamin E supplements only contain alpha–tocopherol, but food sources of vitamin E include γ–tocopherol (a scavenger of reactive oxygen and nitrogen radicals and inhibitor of cyclooxygenase)⁶⁷ and tocotrienols, which have both antioxidant and nonantioxidant benefits that alpha–tocopherol does not possess.⁶⁸

Similarly, patients may be tempted to purchase dietary supplements containing carotenoids (eg, lutein/zeaxanthin) to prevent or treat certain eye diseases (see Cataract and Macular Degeneration ). Although some studies indicate a benefit for supplements, many have found a protective association with carotenoids in foods. The latter may be a preferable source, because macular pigment density increases to a greater degree (43%) when lutein is combined with other antioxidants, compared with lutein alone (36% increase).⁶⁹ Emerging evidence also suggests that higher lutein intake is associated with progression of macular degeneration in the context of diets higher in easily peroxidized polyunsaturated fat (ie, linoleic acid).⁷⁰ Until further data are available, lutein and other micronutrients should be obtained from food primarily, and in supplement form only if recommended by a physician. 

Certain individuals may require nutrients in amounts that exceed RDAs for healthy adults. Such individuals may also benefit from supplementation with nonessential or conditionally essential micronutrients (eg, carnitine, coenzyme Q10).

The following three tables show the relationship between micronutrients and health: Table 1, Conditions That May Be Improved by Nutritional Supplements; Table 2, Vitamin Functions, Deficiency Diseases, Toxicity Symptoms, and Dietary Reference Intakes; and Table 3, Mineral Functions, Deficiency Diseases, Toxicity Symptoms, and Dietary Reference Intakes.